1. Technical Field
The present disclosure relates generally to an organic light emitting diode (OLED) display, and more particularly, to a display device having a peripheral circuit and a display area formed on the same substrate.
2. Description of the Related Art
Active driving or active matrix is a well known method for driving an OLED display using active drive elements. Recently, thin film transistors (TFT) formed by deposition of an insulating substrate on a semiconductor layer has been used as the active drive element. In this way, TFTs have been formed on the insulating substrate to provide a circuit (e.g., driver) formed on an area other than the display area on the insulating substrate. A system formed with a display area and a peripheral circuit (e.g., a driver) together on an insulating substrate is referred to as a system-on-panel (SOP).
In the display device, gamma correction depends on the characteristics of a panel to which a video signal is input. Gamma correction is often a problem when the display device is an organic light emitting diode (OLED) display. An OLED display uses three different organic light emitting materials for each of the respective colors, red (R), green (G), and blue (B), because each organic light emitting material has different characteristics. Therefore, gamma correction is ideally independently applied for each of the R, G, B input signals.
The visibility of an image displayed by a light emitting display device is dependent on the brightness of the ambient environment. Ideally, the light emitting display device should output a brighter image when the ambient environment of the light emitting display device is bright, and output a darker image when the ambient environment of the light emitting display device is dark.
The brightness of an output image of the light emitting display device may be controlled by different methods depending on the brightness of the ambient environment, for example, by gamma correcting each color. However, conventional gamma correction methods use a common reference voltage without regard to the characteristics of the organic light emitting materials of the respective colors (R, G, and B), and accordingly, gamma characteristics cannot be accurately changed to correspond to changes in brightness of the ambient environment.
In the development of the SOP, many attempts have been made to form several circuits on the insulation layer together with the driver. To date, a gamma correction circuit has not been formed on the same insulating substrate.
The information disclosed in this Background section is provided only to enhance understanding the background of the invention and is not an admission that the information is prior art known in this country to a person of ordinary skill in the art.